Contact lens with gaze tracking

ABSTRACT

An eye-mountable device includes an enclosure material, a sensor system, and a controller. The enclosure material has a first surface and a second surface. The first surface is configured to be removeably mounted over a cornea and the second surface is configured to be compatible with eyelid motion when the concave surface is so mounted. The sensor system is disposed within the enclosure material. The sensor system has at least one value that varies with changes in a gazing direction of the cornea. The controller is disposed within the enclosure material and electrically connected to the sensor system. The controller is configured to measure the value of the sensor system to detect the changes in the gazing direction.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present patent application is a continuation of U.S. applicationSer. No. 14/587,664 fled on Dec. 31, 2014, now U.S. Pat. No. 9,442,311,which claims priority under the provisions of 35 U.S.C. §119(e) to U.S.Provisional Application No. 62/012,005, filed on Jun. 13, 2014, entitled“Accommodating Lens,” and to U.S. Provisional Application No.62/012,033, filed on Jun. 13, 2014, entitled “Accommodating LensFabrication.”

TECHNICAL FIELD

This disclosure relates generally to the field of optics, and inparticular but not exclusively, relates to contact lenses.

BACKGROUND INFORMATION

Accommodation is a process by which the eye adjusts its focal distanceto maintain focus on objects of varying distance. Accommodation is areflex action, but can be consciously manipulated. Accommodation iscontrolled by contractions of the ciliary muscle. The ciliary muscleencircles the eye's elastic lens and applies a force on the elastic lensduring muscle contractions that change the focal point of the elasticlens.

As an individual ages, the effectiveness of the ciliary muscle degrades.Presbyopia is a progressive age-related loss of accommodative orfocusing strength of the eye, which results in increased blur at neardistances. This loss of accommodative strength with age has been wellstudied and is relatively consistent and predictable. Presbyopia affectsnearly 1.7 billion people worldwide today (110 million in the UnitedStates alone) and that number is expected to substantially rise as theworld's population ages. Techniques and devices that can helpindividuals offset the effects of Presbyopia are increasingly in demand.

BRIEF DESCRIPTION OF THE DRAWINGS

Non-limiting and non-exhaustive embodiments of the invention aredescribed with reference to the following figures, wherein likereference numerals refer to like parts throughout the various viewsunless otherwise specified. The drawings are not necessarily to scale,emphasis instead being placed upon illustrating the principles beingdescribed.

FIG. 1 is a functional block diagram of an eye-mountable device withcapacitive gaze tracking for auto-accommodation along with an externalreader, in accordance with an embodiment of the disclosure.

FIG. 2A is a top view of an eye-mountable device, in accordance with anembodiment of the disclosure.

FIG. 2B is a perspective view of an eye-mountable device, in accordancewith an embodiment of the disclosure.

FIGS. 3A and 3B illustrate the general operation of a capacitive gazedetection mechanism, in accordance with an embodiment of the disclosure.

FIG. 4 is a flow chart illustrating a process for calibration of acapacitive gaze detection mechanism of an eye-mountable device, inaccordance with an embodiment of the disclosure.

FIG. 5 is a flow chart illustrating a process of auto-accommodationbased upon capacitive gaze detection feedback, in accordance with anembodiment of the disclosure.

FIGS. 6A-E illustrate different capacitance sensor layouts on aneye-mountable device for a capacitive sensor system, in accordance withembodiments of the disclosure.

FIG. 7A illustrates discrete capacitor sensors coupled in parallelbetween a common read-line and a common ground that are implemented withvariable parallel length sections, in accordance with an embodiment ofthe disclosure.

FIG. 7B illustrates discrete capacitor sensors coupled in parallelbetween a common read-line and a common ground that are implemented withinterdigitated fingers, in accordance with an embodiment of thedisclosure.

FIG. 8A illustrates a vertically stacked implementation of a capacitivesensor system and an accommodation actuator, in accordance with anembodiment of the disclosure.

FIG. 8B illustrates an in-plane lateral implementation of a capacitivesensor system and an accommodation actuator, in accordance with anembodiment of the disclosure.

DETAILED DESCRIPTION

Embodiments of an apparatus, system and methods of operation for acontact lens with capacitive gaze tracking and accommodation aredescribed herein. In the following description numerous specific detailsare set forth to provide a thorough understanding of the embodiments.One skilled in the relevant art will recognize, however, that thetechniques described herein can be practiced without one or more of thespecific details, or with other methods, components, materials, etc. Inother instances, well-known structures, materials, or operations are notshown or described in detail to avoid obscuring certain aspects.

Reference throughout this specification to “one embodiment” or “anembodiment” means that a particular feature, structure, orcharacteristic described in connection with the embodiment is includedin at least one embodiment of the present invention. Thus, theappearances of the phrases “in one embodiment” or “in an embodiment” invarious places throughout this specification are not necessarily allreferring to the same embodiment. Furthermore, the particular features,structures, or characteristics may be combined in any suitable manner inone or more embodiments.

Described herein is a smart contact lens or eye-mountable device thatincludes gaze detection circuitry and logic for identifying thedirection or focal distance of a user's gaze and using this informationfor real-time feedback control of an accommodation actuator. Embodimentsof the eye-mountable device may include power supply circuitry, controlelectronics, an accommodation actuator, a capacitive sensor system, andan antenna all embedded within an enclosure material formed to becontact mounted to an eye. The control electronics are coupled tomonitor the capacitive sensor system to identify gaze direction/focaldistance, manipulate the accommodation actuator to control the opticalpower of the eye-mountable device, and provide wireless communicationswith an external reader. In some embodiments, the power supply mayinclude charging circuitry for controlling inductive wireless chargingof an embedded battery.

The enclosure material may be fabricated of a variety of materialscompatible for direct contact with a human eye, such as a polymericmaterial, a hydrogel, PMMA, silicone based polymers (e.g.,fluoro-silicon acrylate), or otherwise. The enclosure material can be inthe form of a round lens with a concave curvature configured to mount toa corneal surface of an eye. The electronics can be disposed upon asubstrate embedded within the enclosure material near its periphery toavoid interference with incident light received closer to the centralregion of the cornea. The capacitive sensor system can be arranged onthe substrate to face outward towards the eyelids to detect the gazedirection/focal distance based upon the amount and position of eyelidcoverage over the capacitive sensor system. As the eyelids coverdifferent portions of the capacitive sensor system, this changes itscapacitance, which can be measured to determine gaze direction and/orfocal distance.

In some embodiments, the gaze direction/focal distance information canthen be used to determine the amount of accommodation to be applied viaa see-through accommodation actuator positioned in a central portion ofthe enclosure material. The accommodation actuator is coupled to thecontroller to be electrically manipulated thereby. For example, theaccommodation actuator may be implemented with a liquid crystal cellthat changes its index of refraction in response to an appliedelectrical bias signal. In other embodiments, the accommodation actuatormay be implemented using other types of electro-active optical materialssuch as electro-optic materials that vary refractive index in thepresence of an applied electric field or electro-mechanical structuresthat change the shape of a deformable lens. Other example structuresthat may be used to implement the accommodation actuator includeelectro-wetting optics, micro-electro-mechanical systems, or otherwise.

FIG. 1 is a functional block diagram of an eye-mountable device 100 withcapacitive gaze tracking for auto-accommodation along with an externalreader 105, in accordance with an embodiment of the disclosure. Theexposed portion of eye-mountable device 100 is an enclosure material 110formed to be contact-mounted to a corneal surface of an eye. A substrate115 is embedded within or surrounded by enclosure material 110 toprovide a mounting surface for a power supply 120, a controller 125, anaccommodation actuator 130, a capacitive sensor system 135, an antenna140, and various interconnects 145 and 150. The illustrated embodimentof power supply 120 includes an energy harvesting antenna 155, chargingcircuitry 160, and a battery 165. The illustrated embodiment ofcontroller 125 includes control logic 170, accommodation logic 175, andcommunication logic 180. The illustrated embodiment of reader 105includes a processor 182, an antenna 184, and memory 186. Theillustrated embodiment of memory 186 includes data storage 188 andprogram instructions 190.

Controller 125 is coupled to receive feedback control signals fromcapacitive sensor system 135 and further coupled to operateaccommodation actuator 130. Power supply 120 supplies operating voltagesto the controller 125 and/or the accommodation actuator 130. Antenna 140is operated by the controller 125 to communicate information to and/orfrom eye-mountable device 100. In one embodiment, antenna 140,controller 125, power supply 120, and capacitive sensor system 135 areall situated on the embedded substrate 115. In one embodiment,accommodation actuator 130 is embedded within enclosure material 110,but is not disposed on substrate 115. Because eye-mountable device 100includes electronics and is configured to be contact-mounted to an eye,it is also referred to herein as an ophthalmic electronics platform,contact lens, or smart contact lens.

To facilitate contact-mounting, the enclosure material 110 can have aconcave surface configured to adhere (“mount”) to a moistened cornealsurface (e.g., by capillary forces with a tear film coating the cornealsurface). Additionally or alternatively, the eye-mountable device 100can be adhered by a vacuum force between the corneal surface andenclosure material 110 due to the concave curvature. While mounted withthe concave surface against the eye, the outward-facing surface of theenclosure material 110 can have a convex curvature that is formed to notinterfere with eye-lid motion while the eye-mountable device 100 ismounted to the eye. For example, the enclosure material 110 can be asubstantially transparent curved disk shaped similarly to a contactlens.

Enclosure material 110 can include one or more biocompatible materials,such as those employed for use in contact lenses or other ophthalmicapplications involving direct contact with the corneal surface.Enclosure material 110 can optionally be formed in part from suchbiocompatible materials or can include an outer coating with suchbiocompatible materials. Enclosure material 110 can include materialsconfigured to moisturize the corneal surface, such as hydrogels and thelike. In some instances, enclosure material 110 can be a deformable(“non-rigid”) material to enhance wearer comfort. In some instances,enclosure material 110 can be shaped to provide a predetermined,vision-correcting optical power, such as can be provided by a contactlens. Enclosure material may be fabricated of various materialsincluding a polymeric material, a hydrogel, PMMA, silicone basedpolymers (e.g., fluoro-silicon acrylate), or otherwise.

Substrate 115 includes one or more surfaces suitable for mounting thecapacitive sensor system 135, controller 125, power supply 120, andantenna 140. Substrate 115 can be employed both as a mounting platformfor chip-based circuitry (e.g., by flip-chip mounting) and/or as aplatform for patterning conductive materials (e.g., gold, platinum,palladium, titanium, copper, aluminum, silver, metals, other conductivematerials, combinations of these, etc.) to create electrodes,interconnects, antennae, etc. In some embodiments, substantiallytransparent conductive materials (e.g., indium tin oxide) can bepatterned on substrate 115 to form circuitry, electrodes, etc. Forexample, antenna 140 can be formed by depositing a pattern of gold oranother conductive material on substrate 115. Similarly, interconnects145 and 150 can be formed by depositing suitable patterns of conductivematerials on substrate 115. A combination of resists, masks, anddeposition techniques can be employed to pattern materials on substrate115. Substrate 115 can be a relatively rigid material, such aspolyethylene terephthalate (“PET”) or another material sufficient tostructurally support the circuitry and/or electronics within enclosurematerial 110. Eye-mountable device 100 can alternatively be arrangedwith a group of unconnected substrates rather than a single substrate.For example, controller 125 and power supply 120 can be mounted to onesubstrate, while antenna 140 and capacitive sensor system 135 aremounted to another substrate and the two can be electrically connectedvia interconnects.

In some embodiments, power supply 120 and controller 125 (and thesubstrate 115) can be positioned away from the center of eye-mountabledevice 100 and thereby avoid interference with light transmission to theeye through the center of eye-mountable device 110. In contrast,accommodation actuator 130 can be centrally positioned to apply opticalaccommodation to the light transmitted to the eye through the center ofeye-mountable device 110. For example, where eye-mountable device 100 isshaped as a concave-curved disk, substrate 115 can be embedded aroundthe periphery (e.g., near the outer circumference) of the disk. In someembodiments, capacitive sensor system 135 includes one or more discretecapacitance sensors that are peripherally distributed to sense theeyelid overlap. In some embodiments, one or more capacitance sensors mayalso be positioned in the center region of eye-mountable device 100.Capacitive sensor system 135 and/or substrate 115 can be substantiallytransparent to incoming visible light to mitigate interference withlight transmission to the eye.

Substrate 115 can be shaped as a flattened ring with a radial widthdimension sufficient to provide a mounting platform for the embeddedelectronics components. Substrate 115 can have a thickness sufficientlysmall to allow the substrate to be embedded in enclosure material 110without adversely influencing the profile of eye-mountable device 100.Substrate 115 can have a thickness sufficiently large to providestructural stability suitable for supporting the electronics mountedthereon. For example, substrate 115 can be shaped as a ring with adiameter of about 10 millimeters, a radial width of about 1 millimeter(e.g., an outer radius 1 millimeter larger than an inner radius), and athickness of about 50 micrometers. Substrate 115 can optionally bealigned with the curvature of the eye-mounting surface of eye-mountabledevice 100 (e.g., convex surface). For example, substrate 115 can beshaped along the surface of an imaginary cone between two circularsegments that define an inner radius and an outer radius. In such anexample, the surface of substrate 115 along the surface of the imaginarycone defines an inclined surface that is approximately aligned with thecurvature of the eye mounting surface at that radius.

In the illustrated embodiment, power supply 120 includes a battery 165to power the various embedded electronics, including controller 125.Battery 165 may be inductively charged by charging circuitry 160 andenergy harvesting antenna 155. In one embodiment, antenna 140 and energyharvesting antenna 155 are independent antennae, which serve theirrespective functions of energy harvesting and communications. In anotherembodiment, energy harvesting antenna 155 and antenna 140 are the samephysical antenna that are time shared for their respective functions ofinductive charging and wireless communications with reader 105.Additionally or alternatively, power supply 120 may include a solar cell(“photovoltaic cell”) to capture energy from incoming ultraviolet,visible, and/or infrared radiation. Furthermore, an inertial powerscavenging system can be included to capture energy from ambientvibrations.

Charging circuitry 160 may include a rectifier/regulator to conditionthe captured energy for charging battery 165 or directly powercontroller 125 without battery 165. Charging circuitry 160 may alsoinclude one or more energy storage devices to mitigate high frequencyvariations in energy harvesting antenna 155. For example, one or moreenergy storage devices (e.g., a capacitor, an inductor, etc.) can beconnected to function as a low-pass filter.

Controller 125 contains logic to choreograph the operation of the otherembedded components. Control logic 170 controls the general operation ofeye-mountable device 100, including providing a logical user interface,power control functionality, etc. Accommodation logic 175 includes logicfor monitoring feedback signals from capacitive sensor system 135,determining the current gaze direction or focal distance of the user,and manipulating accommodation actuator 130 in response to provide theappropriate accommodation. The auto-accommodation can be implemented inreal-time based upon feedback from the capacitive gaze tracking, orpermit user control to select specific accommodation regimes (e.g.,near-field accommodation for reading, far-field accommodation forregular activities, etc.). Communication logic 180 providescommunication protocols for wireless communication with reader 105 viaantenna 140. In one embodiment, communication logic 180 providesbackscatter communication via antenna 140 when in the presence of anelectromagnetic field 171 output from reader 105. In one embodiment,communication logic 180 operates as a smart wireless radio-frequencyidentification (“RFID”) tag that modulates the impedance of antenna 140for backscatter wireless communications. The various logic modules ofcontroller 125 may be implemented in software/firmware executed on ageneral purpose microprocessor, in hardware (e.g., application specificintegrated circuit), or a combination of both.

Eye-mountable device 100 may include various other embedded electronicsand logic modules. For example, a light source or pixel array may beincluded to provide visible feedback to the user. An accelerometer orgyroscope may be included to provide positional, rotational, directionalor acceleration feedback information to controller 125.

It is noted that the block diagram shown in FIG. 1 is described inconnection with functional modules for convenience in description, butdoes not necessarily connote physical organization. Rather, embodimentsof eye-mountable device 100 can be arranged with one or more of thefunctional modules (“sub-systems”) implemented in a single chip,multiple chips, in one or more integrated circuits, or otherwise.

External reader 105 includes an antenna 184 (or group of more than oneantennae) to send and receive wireless signals 171 to and fromeye-mountable device 100. External reader 105 also includes a computingsystem with a processor 182 in communication with a memory 186. Memory186 is a non-transitory computer-readable medium that can include,without limitation, magnetic disks, optical disks, organic memory,and/or any other volatile (e.g. RAM) or non-volatile (e.g. ROM) storagesystem readable by the processor 182. Memory 186 can include a datastorage 188 to store indications of data, such as data logs (e.g., userlogs), program settings (e.g., to adjust behavior of eye-mountabledevice 100 and/or external reader 105), etc. Memory 186 can also includeprogram instructions 190 for execution by processor 182 to cause theexternal reader 105 to perform processes specified by the instructions190. For example, program instructions 190 can cause external reader 105to provide a user interface that allows for retrieving informationcommunicated from eye-mountable device 100 or allows transmittinginformation to eye-mountable device 100 to program or otherwise selectoperational modes of eye-mountable device 100. External reader 105 canalso include one or more hardware components for operating antenna 184to send and receive wireless signals 171 to and from eye-mountabledevice 100.

External reader 105 can be a smart phone, digital assistant, or otherportable computing device with wireless connectivity sufficient toprovide the wireless communication link 171. External reader 105 canalso be implemented as an antenna module that can be plugged in to aportable computing device, such as in an example where the communicationlink 171 operates at carrier frequencies not commonly employed inportable computing devices. In some instances, external reader 105 is aspecial-purpose device configured to be worn relatively near a wearer'seye to allow the wireless communication link 171 to operate with a lowpower budget. For example, the external reader 105 can be integrated ina piece of jewelry such as a necklace, earing, etc. or integrated in anarticle of clothing worn near the head, such as a hat, headband, etc.

FIGS. 2A and 2B illustrate two views of an eye-mountable device 200, inaccordance with an embodiment of the disclosure. FIG. 2A is a top viewof eye-mountable device 200 while FIG. 2B is a perspective view of thesame. Eye-mountable device 200 is one possible implementation ofeye-mountable device 100 illustrated in FIG. 1. The illustratedembodiment of eye-mountable device 200 includes an enclosure material210, a substrate 215, a power supply 220, a controller 225, anaccommodation actuator 230, a capacitive sensor system 235, and anantenna 240. It should be appreciated that FIGS. 2A and 2B are notnecessarily drawn to scale, but have been illustrated for purposes ofexplanation only in describing the arrangement of the exampleeye-mountable device 200.

Enclosure material 210 of eye-mountable device 200 is shaped as a curveddisk. Enclosure material 210 is a substantially transparent material toallow incident light to be transmitted to the eye while eye-mountabledevice 200 is mounted to the eye. Enclosure material 210 is abiocompatible material similar to those employed to form visioncorrection and/or cosmetic contact lenses in optometry, such as apolymeric material, polyethylene terephthalate (“PET”), polymethylmethacrylate (“PMMA”), polyhydroxyethylmethacrylate (“polyHEMA”), ahydrogel, silicon based polymers (e.g., fluoro-silicon acrylate)combinations of these, or otherwise. Enclosure material 210 can beformed with one side having a concave surface 211 suitable to fit over acorneal surface of an eye. The opposite side of the disk can have aconvex surface 212 that does not interfere with eyelid motion whileeye-mountable device 200 is mounted to the eye. In the illustratedembodiment, a circular or oval outer side edge 213 connects the concavesurface 211 and convex surface 212.

Eye-mountable device 200 can have dimensions similar to a visioncorrection and/or cosmetic contact lenses, such as a diameter ofapproximately 1 centimeter, and a thickness of about 0.1 to about 0.5millimeters. However, the diameter and thickness values are provided forexplanatory purposes only. In some embodiments, the dimensions ofeye-mountable device 200 can be selected according to the size and/orshape of the corneal surface of the wearer's eye. Enclosure material 210can be formed with a curved shape in a variety of ways. For example,techniques similar to those employed to form vision-correction contactlenses, such as heat molding, injection molding, spin casting, etc. canbe employed to form enclosure material 210.

Substrate 215 is embedded within enclosure material 210. Substrate 215can be embedded to be situated along the outer periphery of enclosurematerial 210, away from the central region where accommodation actuator230 is positioned. In the illustrated embodiment, substrate 215encircles accommodation actuator 230. Substrate 215 does not interferewith vision because it is too close to the eye to be in focus and ispositioned away from the central region where incident light istransmitted to the light-sensing portions of the eye. In someembodiments, substrate 215 can optionally be formed of a transparentmaterial to further mitigate effects on visual perception. Substrate 215can be shaped as a flat, circular ring (e.g., a disk with a centeredhole). The flat surface of substrate 215 (e.g., along the radial width)is a platform for mounting electronics and for patterning conductivematerials to form electrodes, antenna(e), and/or interconnections.

Capacitive sensor system 235 is distributed about eye-mountable device200 to sense eyelid overlap in a manner similar to capacitive touchscreens. By monitoring the amount and position of eyelid overlap,feedback signals from capacitive sensor system 235 can be measured bycontroller 225 to determine the approximate gaze direction and/or focaldistance. Referring to FIG. 3A, eye-mountable device 200 is disposed ona cornea that is looking straight forward. In this position, capacitancesensors 305 are not overlapped by eyelids 310, which influences theircapacitance value. Controller 225 can determine that the cornea islooking straight forward via the feedback signals from capacitancesensors 305. In this scenario, controller 224 may determine that theuser is focusing on the far-field and the accommodation adjustedaccordingly. Correspondingly (see FIG. 3B), if controller 225determines, based upon the amount and locations of eyelid 310 overlap ofcapacitance sensors 305, that the cornea is looking down and inwardtowards the nose, then it can be assumed the user is focusing on thenear-field (e.g., reading). In this scenario, the amount ofaccommodation applied by accommodation actuator 230 should correspond toa near-field focal distance associated with the activity of reading.

Capacitive sensor system 235 is disposed within enclosure material 210on substrate 215. In the illustrated embodiment, capacitive sensorsystem 235 is distributed peripherally around accommodation actuator230. In the illustrated embodiment, capacitive sensor system 235 isdisposed along the inner edge of substrate 215 between antenna 240 andaccommodation actuator 230. In other embodiments, capacitive sensorsystem 235 may be partially or entirely distributed along the outer edgeof substrate 215 peripherally to antenna 240. Capacitive sensor system235 may be disposed on the backside of substrate 215 adjacent to concavesurface 211 or on the frontside of substrate 215 adjacent to convexsurface 212. Several orientations, groupings, and distributions may beused to implement capacitive sensor system 235. In the illustratedembodiment, capacitive sensor system 235 includes a plurality ofdiscrete capacitance sensors coupled to a common read-line; however,various implementations include a single elongated capacitance sensor, aplurality of discrete capacitance sensors, multiple discrete capacitancesensors coupled in parallel via a common read-line, multiple independentbranches of parallel coupled discrete capacitance sensors, etc. Theseand other implementations for capacitive sensor system 235 are discussedin further detail below in connection with FIGS. 6A-6E.

Accommodation actuator 230 is centrally positioned within enclosurematerial 210 to affect the optical power of eye-mountable device 200 inthe user's center of vision. In various embodiments, accommodationactuator 230 operates by changing is index of refraction under theinfluence of controller 225. By changing its refractive index, the netoptical power of the curved surfaces of eye-mountable device 200 isaltered, thereby applying controllable accommodation. Accommodationactuator 230 may be implemented using a variety of differentelectro-active optical devices. For example, accommodation actuator 230may be implemented using a layer of liquid crystal (e.g., a liquidcrystal cell) disposed in the center of enclosure material 210. In otherembodiments, accommodation actuator 230 may be implemented using othertypes of electro-active optical materials such as electro-opticmaterials that vary refractive index in the presence of an appliedelectric field. Accommodation actuator 230 may be a distinct deviceembedded within enclosure material 210 (e.g., liquid crystal cell), or abulk material having a controllable refractive index. In yet anotherembodiment, accommodation actuator 230 may be implemented using adeformable lens structure that changes shape under the influence of anelectrical signal. Accordingly, the optical power of eye-mountabledevice 200 is controlled by controller 225 with the application ofelectric signals via one or more electrodes extending from controller225 to accommodation actuator 230.

Accommodation actuator 230 may be implemented using a variety ofdifferent liquid crystal structures including nematic liquid crystal,nematic twisted liquid crystal, cholesteric liquid crystal, or bluephase liquid crystal. Since a low switching voltage is desirable for lowpower chip design, nematic liquid crystals with switching voltages lessthan 5 V are suitable. With the application of a 5V control signal,refractive index switching ranging from approximately 1.74 in anoff-mode to 1.52 in an on-mode is achievable. A refractive index shiftof 0.2 should be sufficient to provide near-field accommodation forreading.

Returning to FIG. 2A, loop antenna 240 is a layer of conductive materialpatterned along the flat surface of the substrate to form a flatconductive ring. In some examples, to allow additional flexibility alongthe curvature of the enclosure material, loop antenna 240 can includemultiple substantially concentric sections electrically joined together.Each section can then flex independently along the concave/convexcurvature of eye-mountable device 200. In some examples, loop antenna240 can be formed without making a complete loop. For instances, antenna240 can have a cutout to allow room for controller 225 and power supply220, as illustrated in FIG. 2A. However, loop antenna 240 can also bearranged as a continuous strip of conductive material that wrapsentirely around the flat surface of substrate 215 one or more times. Forexample, a strip of conductive material with multiple windings can bepatterned on the backside of substrate 215 opposite controller 225,power supply 220, and capacitive sensor system 235. Interconnectsbetween the ends of such a wound antenna (e.g., the antenna leads) canthen be passed through substrate 215 to controller 225.

Since eye-mountable device 100 may be used by different user's having avariety of different eye sizes and eyelid shapes, a configurationprocess may be useful to train the system for a particular user.Accordingly, a gaze detection calibration may be executed upon aninitial use (or even on a periodic basis) to acquire baseline readingsfor different gaze directions and focal distances.

FIG. 4 is a flow chart illustrating a process 400 for calibration of acapacitive gaze detection mechanism of eye-mountable device 100, inaccordance with an embodiment of the disclosure. The order in which someor all of the process blocks appear in process 400 should not be deemedlimiting. Rather, one of ordinary skill in the art having the benefit ofthe present disclosure will understand that some of the process blocksmay be executed in a variety of orders not illustrated, or even inparallel.

In a process block 405, controller 125 enters a gaze calibration mode.In one embodiment, gaze calibration mode is activated wirelessly viareader 105. In other embodiments, gaze calibration mode may be activatedvia a particular sequence of eye blinks sensed using capacitive sensorsystem 135. In yet other embodiments, an optical sensor may be includedon substrate 115 to pick up user commands via blink sequences.

Once gaze calibration mode is engaged, the user may be prompted toposition their eyes in a series of gaze directions/focal distances whilebaseline capacitive measurements are acquired. These capacitivemeasurements may be used to both associate baseline capacitance valueswith particular gaze directions and/or focal distances, but also todetermine and/or confirm the rotational position of eye-mountable device100. For rotational-stable contact lenses (e.g., weighted lenses ortoric lenses), positional measurements may not be necessary. Fornon-rotationally stable contact lenses, a position calibration may beperiodically re-executed or continuously monitored.

Process blocks 410 through 430 describe an example calibration sequence;however, it should be appreciated that in various other embodiments theuser may be prompted to look in fewer gaze directions/focal distances,more gaze directions/focal distances, and/or alternative gazedirections/focal distances. In a process block 410, the user is promptedto close their eyelids. In one embodiment, the user may be prompted on adisplay screen or from an audible speaker of reader 105. In otherembodiments, eye-mountable device 100 may include a pixel array capableof providing visual prompts. Once the user closes their eyelids,controller 125 measures the capacitance value(s) of capacitive sensorsystem 135 and stores the capacitance values as baseline referencevalues associated with closed eyelids (process block 415).

In a process block 420, the user is prompted to open their eyelids andlook straight forward at an object that is greater than several metersaway (i.e., far field object). Again, in process block 415, controller125 measures the capacitance value(s) of capacitive sensor system 135and stores the capacitance values as baseline reference valuesassociated with a far-field gaze direction.

In a process block 425, the user is prompted to look at one or moredifferent focal distance by staring at objects at a specified distancefrom the user. Between each prompting, process 400 returns to processblock 415, where controller 125 measures the capacitance value(s) ofcapacitive sensor system 135 and stores the capacitance value(s) asbaseline reference value(s) associated with the prompted focal distance.For example, the user may be asked to read a book and the measuredcapacitance value(s) are then associated with the near-field activity ofreading.

In a process block 430, the user is prompted to look in one or moredifferent directions such as up, down, left, or right. Between eachprompting, process 400 returns to process block 415, where controller125 measures the capacitance value(s) of capacitive sensor system 135and stores the capacitance values as baseline reference value(s)associated with the prompted gaze direction. One or more of themeasurements associated with process block 430 may also be executedindependent of the other process blocks of process 400 to periodicallydetermine the rotational position of eye-mountable device 100 on thecornea.

After all calibration measurements have been acquired, controller 125exits the gaze calibration mode (process block 435).

FIG. 5 is a flow chart illustrating a process 500 for auto-accommodationusing eye-mountable device 100 based upon real-time capacitive gazedetection feedback, in accordance with an embodiment of the disclosure.The order in which some or all of the process blocks appear in process500 should not be deemed limiting. Rather, one of ordinary skill in theart having the benefit of the present disclosure will understand thatsome of the process blocks may be executed in a variety of orders notillustrated, or even in parallel.

In a process block 505, controller 125 enters an auto-accommodationmode. In one embodiment, the auto-accommodation mode is entered intoautomatically after completing a gaze detection calibration. In anotherembodiment, auto-accommodation mode is entered in response to a usercommand receive wirelessly from reader 105 or via a specific blinksequence detected via capacitive sensor system 135 or a photo-detectordisposed on substrate 115 or integrated with controller 125 (notillustrated).

If eye-mountable device 100 is rotationally-stable, such as a weightedor toric contact lens (decision block 510), then process 500 continuesto a process block 515. In process block 515, the capacitance value(s)of capacitive sensor system 135 are measured. In one embodiment, thecapacitance values of capacitive sensor system 135 are constantlymonitored and capacitive changes detected in real-time.

In a process block 520, the measured capacitance value(s) are analyzedby accommodation logic 175 with reference to the baseline valuesacquired during the gaze calibration mode. By comparing the measuredvalues to the baseline calibration values, accommodation logic 175determines the current gaze direction/focal distance of the user's eye.In a process block 525, the amount of accommodation provided byaccommodation actuator 130 is adjusted based upon the determined gazedirection or focal distance. In one embodiment, the accommodationadjustments are automatic and executed in real-time under the influenceof controller 125 and accommodation logic 175. As discussed above,accommodation adjustments are achieved by changing the optical power ofthe central portion of eye-mountable device 100. In one embodiment, thevariable optical power is achieved by manipulating a refractive index ofaccommodation actuator 130. In other embodiments, the variable opticalpower may be achieved by manipulating the shape of a lens. Lens shapemanipulation may be achieved via electrostatically applied force (e.g.,liquid lens) or a mechanically applied force (e.g.,micro-electro-mechanical-system). Other accommodation actuationmechanisms may be implemented.

Returning to decision block 510, if eye-mountable device 100 is not arotationally-stable contact lens, then process 500 continues to aprocess block 530. In process block 530, controller 125 executes anorientation calibration to determine the rotational position (e.g.,which direction is up relative to the eye socket or orbit) ofeye-mountable device 100 on the cornea. In one embodiment, theorientation calibration may include executing the steps described inconnection with process block 430 in process 400 (see FIG. 4). Forexample, the user may be prompted to look up or down and left or right.In other embodiments, eye-mountable device 100 may include one or moreaccelerometers or gyroscopes to determine its rotational direction. Oncethe orientation calibration has been executed, the rotational frame ofreferences of eye-mountable device 100 is updated and temporarily storedfor current operation (process block 535).

In a process block 540, the capacitance value(s) of capacitive sensorsystem 135 are measured. In one embodiment, the capacitance values ofcapacitive sensor system 135 are constantly monitored and capacitivechanges detected in real-time. In a process block 545, the measuredcapacitance value(s) are analyzed by accommodation logic 175 withreference to the baseline values acquired during the gaze calibrationmode and applying adjustments based upon the rotational frame ofreference. By comparing the measured values to the baseline calibrationvalues, accommodation logic 175 determines the current gazedirection/focal distance of the user's eye. In a process block 550, theamount of accommodation provided by accommodation actuator 130 isadjusted based upon the determined gaze direction or focal distance.

In a process block 555, controller 125 monitors or tracks rotationaldrift of eye-mountable device 100 on the cornea to determine if theframe of reference needs to be updated (decision block 560). Dependingupon eye activity, the rate of rotational drift may vary. In oneembodiment, this drift is monitored by monitoring capacitance changes incapacitive sensor system 135. When controller 125 senses the average orbaseline capacitance values of capacitive sensor system 135 have changedby a threshold amount, then it may be determined that eye-mountabledevice 100 has sufficiently rotated to re-execute the orientationcalibration in process block 530. If the average or baseline capacitancevalues have not deviated by the threshold amount, then process 500returns to process block 540 to continue monitoring capacitive sensorsystem 135 for changes. In other embodiments, rotational drift may betracked using embedded accelerometers, gyroscopes, or other mechanisms.

FIGS. 6A-E illustrate different capacitance sensor layouts forimplementing a capacitive sensor system of an eye-mountable device, inaccordance with various embodiments of the disclosure. These capacitivesensor systems represent possible implementations of capacitive sensorsystems 135 or 235 illustrated in FIGS. 1 and 2A.

FIG. 6A illustrates a capacitive sensor system 605 disposed within aneye-mountable device 610. Capacitive sensor system 605 is a singleelongated capacitor that partially encircles accommodation actuator 615.Capacitive sensor system 605 includes a ground electrode 620 and aread-line 625 that is coupled to a controller 630. When the corneamoves, eyelids overlap the elongated capacitor causing its capacitancevalue to change as a continuously changing analog value. Differentcapacitance values can be associated with different gazing directions orfocal distances and thereby used to determine a user's gazing directionor focal distance.

In some embodiments, the separation distance between read-line 625 andground electrode 620 is constant. In other embodiments, the separationdistance between read-line 625 and ground electrode 620 varies withposition. By using a variable separation distance, the linearcapacitance of the capacitor changes along its length. This changinglinear capacitance results in different capacitance changes whenoverlapped by an eyelid at different locations along its length. Thisvariable linear capacitance provides improved differentiation fordetermining both position and amount of eyelid overlap and thereforeimproved capacitive gaze tracking.

FIG. 6B illustrates a capacitive sensor system 635 disposed within aneye-mountable device 640. Capacitive sensor system 635 includes aplurality of discrete capacitance sensors 645 coupled in parallelbetween a common ground (not illustrated) and a common read-line 647.Each discrete capacitance sensor 645 may have the same capacitance valueor a different capacitance value. When the cornea moves, eyelids overlapthe various discrete capacitance sensors 645 causing the totalcapacitance value on read-line 647 to change. Different capacitancevalues can be associated with different gazing directions or focaldistances and thereby used to determine a user's gazing direction orfocal distance. By selecting each capacitance sensor 645 to have adifferent capacitance value, controller 630 has improved differentiationto determine which capacitance sensor 645 has been overlapped by aneyelid. The capacitance values of the different sized capacitancesensors 645 will change by different amounts when overlaid. Capacitivesensor system 635 does not entirely encircle accommodation actuator 615.Rather, in the illustrated embodiment, capacitive sensor system 635 islocated in a lower quadrant closest to a user's nose for arotationally-stable contact lens. It is anticipated that this quadrantwill provide increased sensitivity for distinguishing near-fieldactivities since eyes move down and inward when reading. In oneembodiment, the lower, inner quadrant is populated with a higher densityof capacitance sensor than the other quadrants for increased sensitivityin this region.

FIG. 6C illustrates a capacitive sensor system 650 disposed within aneye-mountable device 655. Capacitive sensor system 650 is similar tocapacitive sensor system 635 illustrated in FIG. 6B, but includes agreater number of discrete capacitance sensors 645 more fully encirclingaccommodation actuator 615. Capacitive sensor system 650 is well suitedfor non-rotationally stable contact lens embodiments since it cannot beanticipated which quadrant of eye-mountable device 655 will end up beingthe lower inward quadrant closest to the user's nose.

FIG. 6D illustrates a capacitive sensor system 660 disposed within aneye-mountable device 665. Capacitive sensor system 660 includes multiplebranches 648 and 649 of parallel coupled discrete capacitance sensors645. Each branch 648 or 649 has an independent read-line connection tocontroller 630. In one embodiment, the multiple branches share a commonground (not illustrated). The capacitance sensors 645 may each have thesame or different capacitance values. Increasing the number ofindependent read-line branches provides greater differentiation todisambiguate between scenarios that cause similar changes in capacitancevalues thereby improving gaze direction sensing. However, this should bebalanced with the cost and complexity associated with increased inputson controller 630 and trace lines. Although FIG. 6D illustrates just twoindependent branches 648 and 649, it should be appreciated that morethan two independent branches may be implemented.

FIG. 6E illustrates a capacitive sensor system 670 disposed within aneye-mountable device 665. Capacitive sensor system 670 includes multiplebranches 648 and 649 of parallel coupled discrete capacitance sensors645. Capacitive sensor system 670 is similar to capacitive sensor system660, except that the capacitance values of each discrete capacitancesensor 645 vary in sensitivity (capacitance) in opposite directionsaround the perimeter of eye-mountable device 675. This configuration isanticipated to discriminate absolute rotational position as well aseyelid coverage.

It should be appreciated that the embodiments illustrated in FIGS. 6A-6Emay be combined into hybrid embodiments. For example, in one hybridembodiment (combination of FIGS. 6A and 6E), two independent elongatedcapacitors may be used, which vary in amount of separation between theirrespective electrodes, but vary in opposite directions along theirlengths. This may be used to provide both eyelid position informationand information about the amount of eyelid coverage. For example, afirst capacitor 1 separation distance between its electrodes may varywith E1(x)=A*x, and second capacitor 2 separation distance between itselectrodes may vary with E2(x)=A*(L−x), where L is the length of theelectrode, A is the rate of scaling, and E1(x) and E2(x) are the amountof electrode separation. In this example, the distance is linearlyscaled. However, distance may instead be scaled in a non-linear ways toprovide linearly or non-linearly changing capacitance changes relativeto eyelid coverage/position.

FIG. 7A illustrates a portion of a capacitive sensor system 701, inaccordance with an embodiment of the disclosure. Capacitive sensorsystem 701 includes discrete capacitance sensors 705A-C coupled inparallel between a common read-line 710 and a common ground 715.Controller 720, read-line 710, and common ground 715 are all disposed onsubstrate 725, which is embedded within an enclosure material of aneye-mountable device. Common read-line 710 is coupled to a single inputinto controller 720. As such, the capacitance value of each capacitancesensor 705A-C adds together for a single collective capacitance valueread via common read-line 710. Capacitance sensors 705A-C areimplemented with variable length sections of read-line 710 that runadjacent and substantially parallel to portions of common ground 715.The variable length sections give each capacitance sensor 705A-C adifferent capacitance value and therefore a different capacitance changewhen overlapped by an eyelid. The distinct change values enablecontroller 720 to determine which capacitance sensor 705A-C has beenoverlaid at a given moment.

FIG. 7B illustrates a portion of a capacitive sensor system 702, inaccordance with an embodiment of the disclosure. Capacitive sensorsystem 702 includes discrete capacitance sensors 706A-D coupled inparallel between a common read-line 711 and a common ground 715.Controller 720, read-line 711, and common ground 715 are all disposed onsubstrate 725, which is embedded within an enclosure material of aneye-mountable device. Common read-line 711 is coupled to a single inputinto controller 720. As such, the capacitance value of each capacitancesensor 706A-D adds together for a single collective capacitance valueread via common read-line 711. Capacitance sensors 706A-D areimplemented with read-line fingers that are interdigitated with commonground fingers. Each capacitance sensor 706A-D has a different number ofinterdigitated fingers resulting in each capacitance sensor 706A-Dhaving a different capacitance value and therefore a differentcapacitance change when overlapped by an eyelid. The distinct changevalues enable controller 720 to determine which capacitance sensor706A-D has been overlaid at a given moment.

In the illustrated embodiments, common ground 715 is implemented bygrounding antenna 140 and time sharing it by controller 720 betweenwireless communications and capacitive gaze sensing. In otherembodiments, common ground 715 may be an independent electrode separatefrom antenna 140. Although FIGS. 7A and 7B only illustrate three or fourcapacitance sensors 705 or 706, more or less parallel coupledcapacitance sensors may share a common read-line.

FIG. 8A illustrates how a capacitive sensor system 805 can be verticallystacked over an accommodation actuator 810, in accordance with anembodiment of the disclosure. For example, capacitive sensor system 805may be implemented with a transparent dielectric layer 815 sandwichedbetween transparent conductive layers 820 and 825. Of course, thetransparent conductive layers 820 and 825 can be patterned into tracesand electrodes to form the read-lines and capacitor electrode terminals.In one embodiment, accommodation actuator 810 is implemented bysandwiching a liquid crystal layer 830 between transparent conductivelayers 825 and 835. In one embodiment, the transparent conductive layers820, 825, and 835 are implemented using indium tin oxide (“ITO”) orother transparent conductors.

FIG. 8B illustrates how a capacitive sensor system 840 can be integratedlaterally in-plane with an accommodation actuator 845, in accordancewith an embodiment of the disclosure. For example, capacitive sensorsystem 840 may be implemented with a dielectric layer 850 sandwichedbetween conductive layers 855 and 860. The illustrated embodiment ofaccommodation actuator 845 includes a liquid crystal layer 865sandwiched between transparent conductive layers 870 and 875. Thelateral in-plane configuration of FIG. 8B enables the use ofnontransparent conductors (e.g., aluminum, gold, etc.) for theconductive layers 855 and 860 forming the capacitor electrode terminals,since the capacitors are positioned along the perimeter of theeye-mountable device.

The processes explained above are described in terms of computersoftware and hardware. The techniques described may constitutemachine-executable instructions embodied within a tangible ornon-transitory machine (e.g., computer) readable storage medium, thatwhen executed by a machine will cause the machine to perform theoperations described. Additionally, the processes may be embodied withinhardware, such as an application specific integrated circuit (“ASIC”) orotherwise.

A tangible machine-readable storage medium includes any mechanism thatprovides (i.e., stores) information in a non-transitory form accessibleby a machine (e.g., a computer, network device, personal digitalassistant, manufacturing tool, any device with a set of one or moreprocessors, etc.). For example, a machine-readable storage mediumincludes recordable/non-recordable media (e.g., read only memory (ROM),random access memory (RAM), magnetic disk storage media, optical storagemedia, flash memory devices, etc.).

The above description of illustrated embodiments of the invention,including what is described in the Abstract, is not intended to beexhaustive or to limit the invention to the precise forms disclosed.While specific embodiments of, and examples for, the invention aredescribed herein for illustrative purposes, various modifications arepossible within the scope of the invention, as those skilled in therelevant art will recognize.

These modifications can be made to the invention in light of the abovedetailed description. The terms used in the following claims should notbe construed to limit the invention to the specific embodimentsdisclosed in the specification. Rather, the scope of the invention is tobe determined entirely by the following claims, which are to beconstrued in accordance with established doctrines of claiminterpretation.

What is claimed is:
 1. An eye-mountable device, comprising: an enclosurematerial having a first surface and a second surface, wherein the firstsurface is configured to be removeably mounted over a cornea and thesecond surface is configured to be compatible with eyelid motion whenthe first surface is so mounted; a sensor system disposed within theenclosure material, wherein the sensor system has at least one valuethat varies with changes in a gazing direction of the cornea; and acontroller disposed within the enclosure material and electricallyconnected to the sensor system, wherein the controller is configured tomeasure the value of the sensor system to detect the changes in thegazing direction.
 2. The eye-mountable device of claim 1, furthercomprising: an accommodation actuator disposed within the enclosurematerial and electrically connected to the controller, wherein thecontroller is configured to electrically manipulate the accommodationactuator to automatically change an optical power of the eye-mountabledevice in response to changes in the value.
 3. The eye-mountable deviceof claim 2, wherein the accommodation actuator comprises a see-throughelectro-active optical material having a refractive index that changesunder electrical influence of the controller.
 4. The eye-mountabledevice of claim 2, wherein the accommodation actuator comprises asee-through liquid crystal layer having a refractive index that changesunder electrical influence of the controller.
 5. The eye-mountabledevice of claim 2, wherein the sensor system comprises: a singleelongated sensor that at least partially encircles the accommodationactuator.
 6. The eye-mountable device of claim 2, wherein the sensorsystem is disposed in a peripheral region of the enclosure material. 7.The eye-mountable device of claim 6, wherein the plurality of discretesensors are arranged into multiple branches with each of the multiplebranches having an independent read-line connection to the controller,wherein the discrete sensors within a given one of the multiple branchesare coupled in parallel with each other.
 8. The eye-mountable device ofclaim 6, wherein the eye-mountable device is a rotationally-stablecontact lens and wherein a density of the discrete sensors is higher ina lower quadrant closest to a user's nose than in one or more otherquadrants of the eye-mountable device.
 9. The eye-mountable device ofclaim 2, wherein the sensor system comprises: a plurality of discretesensors disposed in a peripheral region of the enclosure material. 10.The eye-mountable device of claim 9, wherein the plurality of discretesensors are coupled in parallel with each other and share a commonread-line connection to the controller and share a common ground. 11.The eye-mountable device of claim 10, wherein each of the discretesensors coupled in parallel has a different value that changes by adifferent amount when overlaid by an eyelid.
 12. The eye-mountabledevice of claim 10, wherein the plurality of discrete sensors comprisesvarying a number of read-line fingers that are interdigitated withcommon ground fingers for the different ones of the discrete sensors.13. The eye-mountable device of claim 2, further comprising: a substratehaving a ring shape disposed within the enclosure material, wherein thecontroller and sensor system are disposed on the substrate, wherein thering shape of the substrate encircles the accommodation actuator. 14.The eye-mountable device of claim 2, wherein the sensor system and theaccommodation actuator are disposed with a multi-layer material stackand wherein the sensor system is disposed within the multi-layermaterial stack closer to an eyelid than the accommodation actuator whenthe first surface is so mounted.
 15. The eye-mountable device of claim2, wherein the sensor system and the accommodation actuator are disposedlateral to each other.
 16. A contact lens, comprising: an enclosurematerial having a first surface and a second surface, wherein the firstsurface is configured to be removeably mounted over a cornea and thesecond surface is configured to be compatible with eyelid motion whenthe first surface is so mounted; a sensor system disposed within theenclosure material, wherein the sensor system has at least one valuethat varies with changes in a gazing direction of the cornea; anaccommodation actuator disposed within the enclosure material andlocated to overlay at least a central portion of the cornea when thefirst surface is so mounted; and a controller disposed within theenclosure material and electrically connected to the sensor system andthe accommodation actuator, wherein the controller includes logic thatwhen executed by the controller causes the controller perform operationsincluding: monitoring the value of the sensor system to detect inreal-time the changes in the gazing direction; and electricallymanipulating the accommodation actuator to automatically change anoptical power of the contact lens in response to changes in the value.17. The contact lens of claim 16, wherein the accommodation actuatorcomprises a see-through electro-active optical material having arefractive index that changes under electrical influence of thecontroller.
 18. The contact lens of claim 16, wherein the accommodationactuator comprises a see-through liquid crystal layer having arefractive index that changes under electrical influence of thecontroller.
 19. The contact lens of claim 16, wherein the sensor systemcomprises: an elongated sensor that at least partially encircles theaccommodation actuator.
 20. The contact lens of claim 19, wherein thesensor system is disposed peripherally to the accommodation actuator.21. The contact lens of claim 20, wherein the value of the sensor systemchanges based upon how much an eyelid overlaps the sensor system. 22.The contact lens of claim 20, wherein the eye-mountable device is arotationally-stable contact lens.
 23. The contact lens of claim 16,further comprising: a substrate having a ring shape disposed within theenclosure material, wherein the controller and sensor system aredisposed on the substrate, wherein the ring shape of the substrateencircles the accommodation actuator.
 24. The contact lens of claim 23,further comprising: a battery disposed on the substrate within theenclosure material; and an antenna disposed on the substrate andelectrically connected to the controller, the antenna configured toprovide wireless communication with the controller and inductivecharging of the battery.
 25. The contact lens of claim 24, wherein thecontroller further includes logic that when executed by the controllercauses the controller to perform operations including: alternatelysharing the antenna between wireless communications and as a sensor forgaze sensing.